Project Proposal

Product Dis-Assembly

Causes for Corrective Action

Group 36’s preliminary Project review is to dissect the transmission and engine of a dirt bike. So far the execution is going as planned. All four of the active group members met at the laboratory on the 19th of October and the product was disassembled. As planned, Dan Cocciardi, the group leader, took a visual (both pictures and video) documentation of the whole process as John Flight, the Technical expert, with the aid of Nnamaka Nwufoh took the systems apart. He went step by step, in a chronological order. Eric Dane, the Data Acquisitions coordinator, took a proper written documentation of the process, recording all tools used, every step taken. Nnamaka then bagged and tagged all parts and hardware accordingly. The dissection process was considerably easy, but, it required proper written and visual documentation which took up the most time. The labeling and organization of the parts will greatly expedite the Critical project review stage. The general coordination of the whole process was admirable. Everybody already had their area of concentration, but did not hesitate to help out wherever it was required.
All the teammates of group #36 are at different levels of their academic pursuits, and therefore, different schedules. So, sometimes, getting an all-round schedule that suits everybody might not be feasible. But, due to the commitment the teammates have to outstanding workmanship, they always resolve the situation.
The next time the group will meet will be the 1st of November, 2009 to discuss the next step, Coordination Review of the project.

Management Proposal Overview

This seemed to work out very well. We got the dis-assembly done during the planned times. Individuals did their jobs with competence and in a timely manner. The work load seems to have been distributed fairly.

Review of initial dissection assessment

Basic

a metric socket set will be needed, starting from a 6mm and going up to a 21 mm.

This was correct. All socket wrenches that were needed fell within this range.

a 3/8 ratchet and various sizes of extensions will be needed, starting with a #1 and going up to a #4 just in case some prying becomes necessary.

This proved to be correct. However, it did not go far enough. We needed several other ratchet sizes. We also initially assumed that bolts on the motor would be in Customary Units because bolts attaching the motor assembly to the bike were as such. It turned out that all bolts on the motor were metric. This was easily remedied as all the necessary tools were available. Had they not been, it would have been a considerable set back. We should have prepared for this in advanced.

a box end wrench set will also be needed in the same sizes of the socket set.

This was correct and we had these tools available to us.

Engine and transmission systems

a piston-spring compressor

We used a screw driver in the place of this, it proved to be easy enough and sufficient.

a leather-skin mallet and a bearing press to remove and reinstall the pressed-in bearing.

This step was never undertaken because it was deemed unnecessary.

We stopped disassembling the motor/transmission housing once we got into the transmission and could see it inner workings. This also proved to be true about the clutch and carburetor. We got the motor taken apart to a point where we could tell what was going. In regards to the centrifugal clutch and carburetor, it was decided to use reference material to explain their inner workings because we were unsure if we could get these parts back together should we take them apart.

Misc

a drain pan for the oil inside the motor

Proved to be a major problem. We assumed there would be one available in the lab; there was not. We ended up using a paper cup and a plastic bottle and a entire roll of paper towels. The lack of this basic equipment proved to be a major annoyance throughout the project. If this project did anything in reinforced the basic premise of assume nothing. The simplest things can be the biggest problems.

a chain breaker, in order to remove the engine and transmission from the chassis of the dirt bike.

Proved unnecessary. There was a master link that was removed with a Phillip's head screw driver.

The complete dis-assembly of the dirt bike should take between 2 to 3 hours, in a non-crowded area with full tool availability.

This proved to be spot on. It took us almost exactly three hours to get the bike taken apart.

Unforeseen issues

There was far more oil in the motor than we suspected. We did not plan to let it drain and, as a result, did not let it drain long enough. This made the entire process more complicated then necessary. The main issue was with our own grip - motor oil found its way onto our hands and made gripping objects a hassle. We had to constantly clean our hands off.

Keeping the motor still. There was no vice of any kind we could use to clamp the motor down. This led to precarious situations like someone climbing up onto the table and putting there full body weight on the motor so it would not move when considerable torque needed to be applied.

Not knowing the layout of the motor. Without access to any sort of schematic of the system, taking the motor apart involved more consideration than thought. Several times we reached a point in the dis-assembly where we did not know how to continue. Specifically:

Getting the magneto off. We could not get enough torque on the center bolt holding it in because it (the magneto) spun freely. Several attempts at stopping its rotation by wedging screw drivers into various locations proved ineffective. The best method eventually involved locking pliers, a screw driver and a ratchet. Had a large vice been available, to hold the motor still, many things, including this, would have been easier.

Under the magneto there was a round metal plate that allowed access to the transmission and the sprocket that delivered power to the cam shaft. Getting this off required a #3 screw driver. We had planned to need one. We did not have one in the lab. As such we tried to get it off with a #2 and this proved to be foolish. We eventually found a single #3 screw bit in the lab tools and the TA had the 1/4 drive ratchet in his car we needed to use it. Without that ratchet and that bit the project would have ground to a halt (it took an extra 30 minute fr this anyway.)

Getting the cam shaft and piston housing off required the removal of the chain attached to the sprocket described immediately above. We did not know how to get to this so we considered taking the clutch off. This proved to be very difficult, ran the danger of destroying important gears, and worried us about our ability to reassemble the clutch; we did not want to remove the clutch or take it apart.

Our inability to get the magneto off (as described above) led us on a trial and error journey of deciding how to get one side off (clutch or magneto) so we could access the transmission housing and get the cam shaft chain detached. This proved to be the biggest problem of the dis-assembly. The combination of our ignorance, the lack of a few basic tools we knew we would probably need, the presence of oil on many parts, the lack of a vice to keep the motor from jostling around, and a lack of patience made the process take longer than it needed to.

We arrived at the end of our dis-assembly with a single mystery bolt. As of right now, we are not sure where it went. A momentary lapse in our cataloging procedure caused this and may prove to be of considerable irritation during re-assembly.

Final note - We never foresaw the issue of space and the problem of sharing tools. When we went in to do our dis-assembly, so did five or six other groups. This led to a rationing of tools and space to work. This simply cost more time and effort, as you sometimes had to scour the room for the ratchet or rubber mallet you had a minute ago but now was in the hands of someone else across the room. Further, some people who had already done there dis-assembly were simply inconsiderate. They left there broken down system strewn across one of the four desks in the entire room. When 37 groups are sharing the space, taking up 1/4 of the work space is simply wrong; some people did not even think of this. As such, time was needed to move other group projects, sometime piece by piece, to some place where it could be stored with some degree of order. In our immediate experience, a group left bags of parts, free parts, plastic bags, and tape across a table with no sense of order or concern for the space. This was unforeseen and took up our time.

All issues with the dis-assembly were overcome. The process is described below in the Dissection Procedure

Dissection Procedure

Overview

Figure: Magneto and Output Sprocket Cover

Figure: Head

Figure: Clutch Side Cover

Each step will have a difficulty rating from 1 to 5. A rating of 1 corresponds to a simple task requiring minimal effort, while a rating of 5 corresponds to a task that will require a large amount of effort, several attempts, or assistance from another person.

For the required tools section:

A wrench refers to a ratcheting socket wrench. Socket wrenches are recommended for most of the bolts on the engine and transmission.

A standard open ended wrench may be used on some bolts if preferred, but they will not be useful for most of the bolts. The instructions will explicitly state when an open ended wrench is recommended.

All bolts used on this product are hexagonal.

All bolts should be put into bags and labeled by what part they came from so to not cause confusion during reassembly. Labeling parts with tags or masking tape is also recommended.

Step 1: Drain Oil

Tool(s): 17 mm wrench, drain pan

Difficulty: 1

a. There are several 17mm bolts on the underside of the engine. Remove the bolt on the side closest to the clutch and allow the oil to drain into a container. Allow the oil to drain for 15-20 minutes. There will still be oil on the internal components so paper towels or rags will be beneficial later on for drying off some of the components.

Step 2: Remove Clutch Cover

Figure: Clutch Cover Removed

See: Figure: Clutch Cover Removed

Tool(s): 8 mm wrench

Difficulty: 1

a. There is a metal cover over the clutch mechanism on the engine. Unscrew the two bolts holding it in place, then pull off the cover.

Step 3: Remove Cam Shaft Cover

a. The cam shaft case is the long black ribbed section between the head and the transmission block. On top of the head there is a plate with four bolts and washers at each corner. Remove the bolts and washers and slide off the cover section. Then remove the gasket.

b. On the side opposite the clutch there is another square metal cover panel. There is a round metallic cover directly opposite this panel. There are three bolts fastening the square panel to the cam shaft case, two 8 mm bolts and one 10 mm bolt. Remove the two 8 mm bolts first than the 10 mm bolt. The 10 mm bolt is long and extends all the way through the cam shaft case. Once all these are removed pull off the circular cover mentioned earlier.

c. There are two more circular covers, one on top and bottom of the cam shaft case. These however have a 17 mm bolt head in their center. These two covers require more force to loosen than the previous bolts so a vise or additional person will be needed to hold the engine steady. A rubber mallet can be used to strike an open ended wrench attached to the bolt as another method to loosen.

d. Underneath the metallic disk is a nut on a screw. Use a 9 mm wrench to remove the nut. This must be done for the top and bottom openings

Step 4: Remove Spark Plug

Figure: Spark Plug

See: Figure: Spark Plug

Tool(s): 16 mm wrench

Difficulty: 1

a. The spark plug is long so a deep socket will be required. The socket must be long enough to fit the spark plug and reach the bolt at the bottom, (at least 2.5 inches.)

Step 5: Remove Magneto Side Case

Figure: Magneto Cover

See: Figure: Magneto Cover

Tool(s): 8 mm wrench, Flathead screwdriver

Difficulty: 3

a. On the opposite side of the clutch there is another cover protecting the magneto and transmission output sprocket. There are 10, 8 mm bolts surrounding the perimeter of the casing. Loosen and remove each of these screws.

b. Once the screws are removed the section of casing must be pried off. A Flathead screwdriver is recommended or some other tool that can be used to get into the space between case sections to obtain some leverage. There is a gasket that must also be taken off after the casing is removed.

Step 6: Remove Kick Start and Selection Lever

Figure: Selection Lever

See: Figure: Selection Lever

Tool(s): 10 mm wrench, Flathead screwdriver

Difficulty: 3

a. The selection lever is on the clutch side of the engine (the lever that changes gears). There is one 10 mm blot that must be removed then the lever slides off.

b. Once the selection lever has been removed the selection linkage will slide off.

c. A 10 mm bolt must be removed on the kick start (located on the opposite side as the selection lever). There is a tighter fit with the kick start so the Flathead screw driver will be needed to help pry the kick start loose so that it can be removed.

Step 7: Remove Sprocket

Figure: Sprocket and Magneto

See: Figure: Sprocket and Magneto

Tool(s): 10 mm wrench

Difficulty: 1

a. There are two bolts holding the sprocket (output shaft of transmission) to the transmission. Remove the bolts, slide off the sproket, and remove the gasket.

a. There are two phillip’s screws and a 14 mm bolt holding the magneto in place (the magneto is the circular component that is on the side opposite the clutch). Remove the two screws first.

b. To remove the 14 mm bolt the round clutch mechanism on the other side must held to prevent it from rotating. Have another person clamp down on the mechanism with the locking pliers to hold it in place. Once this is done try loosening the bolt. It may also be useful to clamp down the entire motor to stop any addition rotation. Remove the bolt once it is unscrewed.

c. Pry the magneto off once all the screws and bolts are removed. A flathead screwdriver can give some additional leverage and a rubber mallet can be used to apply additional force.

d. Underneath the magneto is a wire coil held in place by two additional phillip’s head screws. Unscrew these two screws.

e. There is also wiring under the magneto. There are two clips around the wiring, which are spot welded to the transmission case. Use the flathead screwdriver and rubber mallet as a hammer and chisel to break the welds.

f. There is a metal plate with two more phillip’s head screws on this side of the motor. Use the #3 screw head and ¼ in drive ratchet to remove these screws. Make sure to use these specific tools because they create a tight fit and allow for enough force to remove the screws without stripping them.

g. In the middle of these two screws is a bolt. Remove it with a 10 mm wrench. Once this is done the metal plate they were holding in place can be removed.

Step 9: Remove 17 mm bolt

Tool(s): 17 mm wrench

Difficulty: 3

a. In the first step a bolt was removed to drain the oil. Go back to this region of the motor and there should still be another bolt on the opposite side of the motor from Step 1. Under this bolt is a spring. The bolt must be loosened and pressure must be applied to it as it slides out so that the spring does not shoot out of the hole. Once the spring is no longer compressed the bold and spring can be taken out.

Step 10: Remove Tensioner

Figure: Tensioner

Tool(s): 17 mm wrench, rag

Difficulty: 2

a. There is a single black bolt on the inside of the transmission. Use a 17 mm wrench to remove it.

b. If you follow the bolt hole from Step 10 to the inside of the transmission you should find a metal rod. This is the tensioner. Slide the tensioner up through the Step 10 bolt hole. There will most likely be oil in the bolt hole that will come out as the tensioner is slid up. Use the rag to wipe up the oil as it spills out.

Step 11: Removing Cam Shaft (Header)

Figure: Camshaft Sprocket

Tool(s): 8 mm wrench, screwdriver

Difficulty: 4

a. During Step 3 there was a circular metallic cover that was removed and underneath there was a chain attached to a gear. Go back to this area and remove the three bolts around the center of the gear with an 8 mm wrench.

b. Once the bolts are removed the chain around the gear must be taken off to remove the gear. This part can be difficult since there is little room to move the gear and chain around. Use a screwdriver for assistance and keep shifting the gear and chain around until they separate then remove the gear.

c. The chain connects to another gear inside the transmission body. Take the chain off this gear and pull it the cam shaft casing and out the transmission.

d. Now that the chain has been removed the head can be removed.

e. The black sleeve below the head can now be removed, along with the piston head contained inside. This exposes the cam shaft.

Step 12: Remove Piston Head

Figure: Crankshaft

Tool(s): x2 Flathead screwdriver (or pliers)

Difficulty: 2

a. There is a pin connecting the piston head to the rod. Remove it by prying it apart with the two screwdriver (or with small pliers, pry them apart.)

b. Remove pin by hand. (Will slide out easily)

c. Remove piston head.

Step 13: Remove Transmission Case

Tool(s): 8 mm wrench, rag

Difficulty: 1

a. There are seven more bolts around the perimeter of the transmission case. Loosen and remove all of these with the 8 mm wrench.

b. Pry open the transmission case using the Flathead screwdriver in the same manner as mentioned in Step 6.

c. Slide off the central section of the transmission case.

Figure: Inside Transmission

Figure: Split Transmission Case

Product Documentation and Analysis

Component Summary

Component List

L - length of cylindrical section of screw or bolt

D - larger diameter for that part

d - smaller diameter for that part

A magnet was used to determine whether a part was made of aluminum or steel. This is because aluminum is not magnetic, but steel for the most part is. Only some specific steel alloys are not magnetic, but these alloys are not present in this engine.

The component complexity is rated on a scale from 1-5 where 1 is simple and 5 is complex. The rating will be determined by evaluating several factors which include number of parts and how difficult it was to manufacture the process.

Since the components being analyzed here are all parts of an engine the vast majority of them are functional. This is because they will not be seen and it is much more important to have the internal workings of an engine be efficient than to look good. The only part that has any real reason to be cosmetic would be the transmission casing. The clutch cover does have some cosmetic touches such as the sleek shape and it also has the name of the company. The transmission housing as a whole is smooth and sleek, but is still a functional part because it is smooth to reduce drag and to prevent the rider from injuring themselves on it. The housing itself is also meant to be for structural support and protection.

All bolts and screws used were made of steel.

Component: Inner Left Transmission Case

Figure:Clutch

See: Figure:Clutch

Function: It houses transmission, protects it from dirt and debris, and provides support for the axles to keep them in place. It also keeps the engine in place using two metal rods that slide through holes through the cylinder and valve assembly sections.

Material: Aluminum is used for the vast majority of the component. The rods are steel with a copper coating. The rolling element bearings are steel. The spur gear in this casing is made of a hard rubber interior and has a steel outer ring and spurs.

Manufacturing Process: The casing was mold casted. The holes for the screws were drilled after the cast was made. Some of these holes were tapped. The two rods were drawn to the desired diameter and then threaded at the end with a die. The two bearings in the casing were assembled outside then glued into indentations in the case. The gear was machined by drilling and milling.

Model/Part Number: N/A

Miscellaneous Information: One of the indentations fitted for an axel contains a caged radial ball bearing whose components were machined and then assembled to the casing. Another indentation in the casing for an axel has a thrust bearing with cylindrical rollers made and used in a similar way to the ball bearing.

Part Count: 1

Fasteners

2 hexagonal washer bolts L=60 mm D=10 mm d=6 mm

1 hexagonal washer bolt L=48 mm D=10 mm d=6 mm

4 hexagonal washer bolts L=64 mm D=10 mm d=6 mm

Complexity: 2 This component is not very complex. It does not contain many parts and can be easily manufactured.

Component: Inner Right Transmission Case

Figure: Transmission (Front View)

See: Figure: Transmission % Transmission (Front View)

Function: It houses the shafts and gears of the transmission and keeps them in place. It also contains two rods used to hold the cylinder and valve assembly sections in place.

Material: The case is made of aluminum. The rods are steel and are coated in copper.

Manufacturing Process: The casing was mold cast as then the holes were machined into it. Some of these holes were then tapped. The two rods were drawn to the desired diameter and then threaded at the end with a die.

Model/Part Number: N/A

Miscellaneous Information: The transmission, crank shaft, the shaft for power output, magneto shaft, and the centripetal clutch are all held to this section of the transmission housing.

Part Count: 1

Complexity: 4 This part is reasonably complex. Unlike the inner left housing, this section holes drilled through it to support all the shafts. It also has to keep all crank shaft and transmission balanced. It requires more machining after the initial cast.

Component: Transmission

Figure: Transmission

See: Figure: Transmission

(The transmission parts were pressed together they were not completely disassembled and will be counted as a single component)

Function: It is used to transfer the power from the engine to the drive chain.

Material: Steel is the main material making up the gears and axels. There is one spring that is made of copper.

Manufacturing Process: The gears are machined using a variety of processes including drilling for the center hole, milling for the spurs, and broaching for the key ways. The axles are machined to the desired diameter using a lathe. They are also milled to have the splines put on. The spring is machined into the coil shape.

''Model/Part Number: N/A

Miscellaneous Information: The transmission assembly also includes copper and steel spacers between some of the gears and there are two steel brackets put in place for support.

Part Count: 10 gears, 3 shafts, 1 spring

Fasteners

2 copper spacers

3 steel spacers

2 brackets

Complexity: 5 This is a very complex component with a lot of moving parts. Each gear must be able to smoothly lock into place and also change which gear they are locked into. Each part also needs to be a precisely machined.

Component: Shifting Mechanism

Figure: Shifting Attachment

Figure: Shifter

See: Figure: Shifting Attachment & Shifter

Function: Used to change what gear the dirt bike is in.

Material: All parts are made of steel. There is a section on the selection lever made of rubber.

Manufacturing Process: These parts were all machined. The sprocket was drilled and milled and the shaft was lathed to the desired diameter. The longer gear select mechanism part was pressed into shape and the cylindrical protrusion was welded on. The rounder part was pressed as well. The select arm was cast molded as two parts then welded together.

Model/Part Number: N/A

Part Count: 1 sprocket, 1 spring, 1 axel, 1 select lever

Fasteners

1 hexagonal full thread tap bolt L=20 mm D=9 mm d= 5 mm

Complexity:3 Some of the parts for the shifting mechanism are uniquely shaped and therefore need a more intricate machining process. However there are not too many parts to this component, which keeps it from being too complex.

Component: Piston Housing

Function: It is the cylinder that encloses the piston and is the site of combustion.

Material: Aluminum except for the internal cylinder which is made of steel.

Manufacturing Process: The part is mold caste and there are several holes that are drilled. The interior cylinder looks machine finished (ground smooth). One of the holes was tapped.

Model/Part Number: N/A

Miscellaneous Information: The fin-like protrusions appear to be a way to disperse heat from the part.

Complexity: 2 This is a very simple part because it can be easily manufactured. The only real complexity is because of the need for different materials between the interior cylinder and the housing.

Component: Outer Left Transmission Case (Magneto Cover)

Figure: Magneto Cover

See: Figure: Magneto Cover

Function: To cover and protect the magneto and other components on the left side of the transmission.

'Material: aluminum

Manufacturing Process: mold caste

Model/Part Number: N/A

Miscellaneous Information: N/A

Part Count: 1

Fasteners

1 hexagonal washer bolt L=28mm D=10 mm d= 5 mm

1 hexagonal washer bolt L=35mm D=10 mm d=5 mm

Complexity: 1 This housing requires minimal machining and has no moving parts.

Component: Outer Right Transmission Case (Clutch Cover)

Figure: Clutch Cover & Kick-Start

'See: Figure: Clutch Cover & Kick-Start

Function: To cover and protect the clutch and other components on the right side of the transmission.

Material: aluminum

Manufacturing Process: mold cast

Model/Part Number: N/A

Miscellaneous Information: N/A

Part Count: 1

Fasteners

1 hexagonal washer bolt L=80 mm D=10 mm d=6 mm

2 hexagonal washer bolts L=64 mm D=10 mm d=6 mm

5 hexagonal washer bolts L=40 mm D=10mm d=6 mm

Complexity: 1 Like the magneto cover, the clutch cover can be easily manufactured and contains no moving parts.

Component: Magneto/Stator Plate

Figure: Magneto

Figure: Stator

Figure: Stator Plate

See: Figure: Magneto, Stator & Stator Plate

Function: Generates the voltage required by the spark plug to create the spark.

Material: The magneto is made of magnetized steel and brass. The Stator plate is aluminum and the wire coil is copper. A steel bracket is used to hold the wire coil.

Manufacturing Process: The magneto is made of two layers of metal and were forged together to make a single cylinder. These two sections were also riveted together. The center hole is splined with a broach. The stator plate was mold casted and had several holes drilled into it. These holes were tapped. The wire was drawn to its desired diameter and then wrapped to make a coil.

Model/Part Number: N/A

Fasteners

1 nut L=11 mm d=10 mm

Part Count: 1 magneto, 1 wire coil, 1 stator plate

Fasteners

2 Phillips round head screws D=10 mm

2 lock washers D=7 mm

2 Phillips flat head screws D=12 mm d=6 mm

Complexity: 4 This component has several parts and requires wiring. The magneto itself is also made of a magnetic material and is put together in a way that no other part of the dirt bike is put together.

Component: Crank Shaft and Connecting Rod

Figure: Transmission

See: Figure: Transmission

Function: Used to convert the power generated during combustion into mechanical power.

Material: steel

Manufacturing Process: The connecting rod is machine pressed. A lathe is used to cut the crank shaft to the desired diameter and to taper it down at one end. Threads were also cut into the shaft most likely with a lathe. The flywheels are cut from some cylindrical stock and then milled to the desired shape. They must also be drilled to create the axle slot.

Model/Part Number: N/A

Miscellaneous Information: There are two flywheels that “sandwich” the connecting rod. Additionally there is a ball bearing on both sides of the flywheel. The crank shaft is connected to the clutch, which is on the other side of the inner right transmission case.

Complexity: 4 There are several parts to this component that have unique manufacturing requirements. The flywheels must be made to have an uneven distribution of weight and the connecting rod has a more complex way to connect to the crank shaft than just sliding on. The parts are also in motion.

Component: Valve assembly

Figure :Valves

See: Figure :Valves
(See also Figure: Spark Plug/Valve Covers)

Function: Allows fuel/air mixture to enter the engine and exhaust to leave the engine at the desired times.

Material: The outer cast is aluminum as well as the valve heads. The inner components are steel. The covers are also made of steel.

Manufacturing Process: The outer casing was mold caste. The case also consists of two rectangular covers that were mold caste and then machined. There is another circular cover that was pressed into its shape. The inner parts were machined by milling and drilling and were grind finished. Once the parts were made the entire assembly would be put together.

Model/Part Number: N/A

Miscellaneous Information: The interior components include two arms to engage the valves, valve stems including a spring in each, two ball bearings, axel, intake and exhaust ports, and fin-like heat vents like the ones on the cylinder casing.

Complexity: 5 This part is complex because it has many moving parts that are all in close proximity. There are also several manufacturing processes that are used on all the parts. It also requires the parts to move during specific times.

Component: Head Gasket

Figure: Head Gasket

Figure: Head Gasket (Detached)

See: Figure: Head Gasket & Head Gasket (Detached)

Function: Seals the cylinder

Material: Plastic with a steel ring.

Manufacturing Process: machined with drills and mills.

Model/Part Number: N/A

Miscellaneous Information: N/A

Part Count: 1

Fasteners

2x sleeve L=14 mm d=7 mm

1x flanged sleeve L=10 mm d= 10 mm

1x rubber spacer d=19 mm

1x rubber spacer d=17 mm

1x washer D=15 mm

1x washer D=26 mm d=14 mm

Complexity: 1 Very simple manufacturing process and it only has two parts.

Component: Piston Head

Figure: Piston Head

See: Figure: Piston Head

Function: Creates the pressure barrier for during the combustion process and transfers that energy to the connecting rod.

Material: Aluminum with a steel cap on the side where combustion occurs.

Manufacturing Process: Various machining processes are used including milling, drilling, and pressing.

Model/Part Number: N/A

Miscellaneous Information: N/A

Part Count: 1

Complexity: 3 Though this component only has one part it has a complex manufacturing process that would require several steps. It is also made of two materials.

Component: Chain and Chain Tensioner

Figure: Chain and Tensioner

See: Figure: Chain and Tensioner

Function: Connects the cam shaft in the valve

Material: The arm of the tensioner is made of steel. The pulley guide and cam shaft sprocket are made of hard rubber. The chain is also made of steel.

Manufacturing Process: Pulley and spur gear were mold caste. The arm of the tensioner was pressing into its shape. The holes were drilled and rounded sections were milled. The chain was assembled after its individual sections were machined.

Complexity: 3 None of the parts aside from the chain are very intricate, but there are enough parts that require a decent amount of manufacturing to make the total assembly somewhat complex.

Component: Clutch

Figure:Clutch

See: Figure:Clutch

Function: The clutch transfers power to the transmission when it is engaged and allows the engine to turn without transmitting power to the transmission when it is disengaged.

Material: Steel and a break pad

Manufacturing Process: machined

Model/Part Number: N/A

Miscellaneous Information: The clutch is composed of many parts, but is generally made of three important sections. These are the flywheel, clutch disk, and the pressure plate. The flywheel is connected to the crank shaft. The clutch pressure plate is what gets engaged and disengaged when the clutch lever is pulled. The pressure plate is when applies the force to the clutch disk for engaging and disengaging.

Part Count: 1 flywheel, 1 clutch disk, 1 pressure plate (There are more components to each of these sections, but the exact components are unknown because it was not disassembled due to difficulties in reassembly)

Fasteners

4x Phillips round head screws L=12 mm D=9 mm d=5 mm

4x spacers

4x washers D=15 mm d=5 mm

Complexity: 4 There are only three major components to the clutch, but each component requires a lot of machining. There are also several smaller parts that increase the complexity of this component.

Component: Drive Chain Sprocket

Figure: Sprocket

See: Figure: Sprocket

Function: Final gear that puts the power from the transmission into the drive chain to rotate the rear wheel.

Material: steel

Manufacturing Process: Machined by drilling and milling

Model/Part Number: N/A

Miscellaneous Information: N/A

Part Count: 1

Fasteners

1x sprocket spacer

2x hexagonal full thread tap bolts D=10 mm

Complexity: 1 This is just a standard gear. It requires several machine processes, but is because it is only a single part it is not difficult to manufacture.

Component: Spark Plug

Figure:Spark Plug/Valve Cover

See: Figure:Spark Plug/Valve Cover

Function: Creates the spark for ignition in the cylinder.

Material: steel and plastic

Manufacturing Process: parts are machined and assembled

Model/Part Number: Torch A7RTC

Miscellaneous Information: N/A

Part Count: 1

Complexity: 3- Though it is only one part it has many sections including the terminal, ribs, insulator, casing, seals, threads, and electrodes. This entire assembly would require a decent amount of work to put together.

Component: Drain Pipe

Function: to drain the oil

Material: rubber

Manufacturing Process: mold cast

Model/Part Number: N/A

Miscellaneous Information: N/A

Fasteners

1x washer D=16 mm d=9 mm

1x nut D=14 mm d=8 mm

1x mount

Complexity: 1- plane rubber tubing.

Component: Oil Plug

Figure: Oil Plug

See: Figure: Oil Plug

Function: For refilling the oil

Material: plastic

Manufacturing Process: machined

Model/Part Number: N/A

Miscellaneous Information: N/A

Part Count: 1

Complexity: 1- Simple plastic component

Component: Spring Tensioner

Figure: Tensioner

See: Figure: Tensioner

Function: applies tension to the spring

Material: aluminum and has a rubber cap

Manufacturing Process: The tensioner has holes that are drilled and lathing is used to achieve the desired diameter. The spring is coiled wire.

Model/Part Number: N/A

Miscellaneous Information: N/A

Part Count: 1 tensioner, 1 spring

Fasteners

1x hexagonal full thread washer bolt L=14 mm D=16 mm d= 10 mm

1x mount

Complexity: 1- requires only basic machining processes

Component: Drain Bolt

Figure: Oil Plug

See: Figure: Oil Plug

Function: drains oil

Material: steel

Manufacturing Process: machined milling and a die was used for the threading

Model/Part Number: N/A

Miscellaneous Information: N/A

Fasteners

(This part is a fastener)

Complexity: 1- simple bolt

Component: Kick Start

Figure: Clutch Cover & Kick-Start

See: Figure: Clutch Cover & Kick-Start

Function: Initial power used to start the engine.

Material: Steel

Manufacturing Process: mold caste and machine finished. The hole in the lever was drilled and then the splines were broached.

Model/Part Number: N/A

Miscellaneous Information: The kick start is composed of four parts. It has two arms hinged together to make an “L” shape. There is also a bolt and washer.

Part Count: 1 kick start

Fasteners

1x hexagonal full thread tap bolt L= 23 mm D= 9 mm d= 5 mm

1x washer D= 20 mm d= 10 mm

1x lock washer D= 20 mm d= 10 mm

Complexity: 2- made of two parts, but is mold caste and requires only simple machining

Design Revisions

This system appears to be very well constructed (as judged by our limited knowledge.)Finding necessary improvements to the motor and transmission is difficult.

A primary revision that would be of great value to anyone who has ever used a screwdriver is simple, change all Philips head screws to Allen or slotted head screw. These screws are available, the price is comparable, and the chance of stripping a tightly set screw decrease.

A second revision would be to move the oil drainage port or create another one. It seems that the port is positioned too high to allow all the oil to drain out of the transmission casing. In order to fully drain it, the transmission casing must be tilted nearly 90 degrees from its normal position. If a port was positioned at the rear of the casing, it would most likely make this drainage process easier.

The third suggestion would require some testing. The magneto and ignition coil are positioned directly opposite of the centrifugal clutch. Sitting flush with the clutch is the main drive wheel in the transmission which transferes power from the crank to the transmission. If the magneto could be made slightly smaller in its diameter and height, it could be positioned above this sprocket. This would decrease the overall volume of the motor and allow it to be shifted toward the side the magneto is currently on. This would give more room for the drivers legs (allowing for the avoidance of the 'bow' legged position you must take on the bike, at least to some degree) make the bike lighter and most likely reduce the drag to some small degree.

This suggestion would require testing because it would change the center of gravity of the whole system and change the stresses on the new gear to which it is attached.

AutoCAD Model

Engineering Analysis

Question: Choose a key component or function and explain how engineering analysis would be used in the design or testing stages of the design process. Provide a detailed description including relevant equations and processes that would allow an engineer to easily perform analysis.

Relevant Equation:

V = L dI (Equation 1)

Where:

V = Voltage (V)

L = Inductance (H)

dI = The rate of change of the current (A).

Ignition Coil
"An ignition coil is essentially an auto transformer with a high ratio of secondary to primary windings. An "Auto-transformer" is a set of primary and secondary windings are not actually separated - they share a few of the windings"
(How to use an Ignition Coil,http://www.sentex.net/~mwandel/cannon/sparky.html )

In the bike, the Ignition coil is designed to pick up magnetic signals whenever a Magnet crosses the coils’ pickup point. (This is located under the magneto, which rotates by taking mechanical energy from the crankshaft.) The changing magnetic field generates a voltage, which in turn, supplies energy for the spark plug to ignite fuel. The coil is grounded to stop the spark plug from multiple ignitions after start-up.
The actual spark is generated when the breaker contacts open. For an ideal inductor, the current and voltage relate by Equation 1.

Since L is constant for the inductor, the abrupt change in current will cause a very short, very high voltage spike.

Analysis and Testing: Given the equation above, it is possible to test the ignition coils ability to supply a voltage by measuring the resistance of the low tension (secondary winding) and high tension (primary winding) wires and the ground (the ground for the wires is the coil-mounting bar that passes through the coil and mounts it to the frame.). There should be a huge difference in the resistance value. The low-tension wire should show a small value on the magnitude of a single ohm. The high-tension wire, which goes to the spark plug, should show a resistance on the order of several thousand ohms. The circuit for this system is relatively simple
(see Diagram 1).

Creating this circuit with the proper resistance values would take basic engineering analysis in the testing stages. A multi-meter and a voltage supply would be needed to test the circuit’s connectivity and resistance values. Verifying that the circuit was connected according to the design and the resistance values were in the correct range could be found with a multi-meter. If it was found that the spark plug was not receiving enough energy to ignite the fuel, the coil could be changed such that the high-tension line had a larger inductance value and tested again.

Product Reassembly

Note: All images are the same as the ones presented in assembly and analysis.

As in the dis-assembly process, socket wrenches were used for the majority of the procedure. They will be referred to as wrenches unless otherwise noted in the tools section of each step.

Difficulty scale is from 1-5 where 1 is a simple step and 5 is a difficult step.

Step 1: Inner Left Transmission Housing

Tools: 8 mm wrench

Fasteners:

2x 8 mm hexagonal washer bolt of length 60 mm

1x 8 mm hexagonal washer bolt of length 48 mm

2x 8 mm hexagonal washer bolt of length 64 mm

Difficulty: 2 This step can be somewhat difficult because some of the shafts require some effort to get into the correct position. Other than that it is straight forward.

a. Slide the inner left transmission housing onto the inner right transmission housing. All the shafts must line up and go through their respective holes in the housing. The idea is simple, but it might take some time to get it back on. It is recommended that two people do this step. One can adjust the shafts to make the sure they are going into their slots while the other people applies pressure to the two parts so that they come together.

b. Once together put the six washer bolts back into their respective holes. It does matter which ones go where because some of the bolt slots are deeper than others. Just make sure that when they are being put back that the bolt reaches the threaded part of the hole and that there is no excess bolt hanging out of the hole.

Step 2: Piston Head

Tools: flat head screw driver

Fasteners: N/A

Difficulty: 2 The steps are not particularly difficult, but there is a chance to lose parts. It can also get difficult to line all the parts up without assistance.

a. There is a shaft that runs through the piston head. There are two rings that keep the shaft from just sliding out of the piston head. These rings are located at either end of the shaft. Use a flat head screw driver to press down and out on the ring to pry it out. Note: You will need to use a significant amount of force to do this and therefore the ring will most likely shoot out of the piston head. Be sure to block the ring from flying off so that you do not lose it. Eye protection may also be a good idea.

b. Once the ring is removed slide the shaft out. Line the shaft slots on the piston head up with the hole on the connecting rod. Slide the rod through the lined up holes and then force the ring back into place. Again this will be much easier to do with assistance as one person can line up the holes while the other slides the shaft in.

Step 3: Cylinder Housing

Tools: 10 mm wrench

Fasteners:

1x hexagonal full thread washer bolt with Phillips slot

Difficulty: 2 The only part that adds difficult part to attaching this section is to compress the rings around the piston head so that is can fit into the cylinder.

a. Take the black cylinder housing component and slide it down the four copper colored rods that are surrounding the piston head. The cylinder protruding from the housing slides down first and fits into the transmission housing. Also make sure the rectangular slot is on the left side of the housing. There are rings around the piston head that must be compressed so that it can fit into the cylinder. A two person system where one person compresses the rings while another pushes the cylinder housing is recommended. Note: Putting oil on the inside of the cylinder is recommended so that when the rings on the piston head expand to fill the cylinder they don’t scratch and damage it.

b. There is a threaded hole on the housing that lines up with a threaded hole in the transmission housing. Put the bolt mentioned in the fasteners section into this slot and tighten.

Step 4: Tensioner Assembly

Tools: 17 mm wrench

Fastener:

1x 17 mm black bolt

1x 7 mm full thread washer bolt

1x 17 mm silver washer bolt

Difficulty: 4 There are a lot of parts involved in this step of reassembly one of which is a spring that can make this difficult. It is highly recommended to do this part of the assembly with another person.

a. First make sure all the parts for the assembly are on hand. There should be an armature with rubber gear attached, a rubber pulley, the timing chain, a tensioner rod, and a spring with tapered diameter at one end. This assembly is going to be placed in the circular “window” in the inner left transmission housing.

b. Position the black bolt through the hole in the armature. Screw the bolt into the bolt slot in the up right side of the “window” so that the gear is on the left (above the gear that was attached to the transmission housing) and the rounded metal end of the armature is to the right.

c. There is a bolt slot on the underside of the transmission housing that feeds all the way into the area where the tensioner assembly is going to be. Put the tensioner rod into this slot so that the rubber end of the rod will end up inside the assembly area and the metal end will be inside the slot. Take the spring and put in the slot so that the tapered end is in contact with the tensioner rod. Compress the spring with the silver bolt and then screw the bolt into the slot. If done correctly the rubber part of the tensioner rod should be in contact with the armature.

d. Take the chain and loop it around the crank shaft. There is a gear on the shaft that the chain meshes with. Feed the chain through the slot on the cylinder housing. The chain should also be able to mesh with the other two gears, the one attached to the armature and the one attached to the transmission housing.

e. There is a threaded slot on the cylinder housing that goes into the rectangular slot. The pullet goes into the rectangular slot and the 7 mm bolt goes through the threaded slot and holds the pulley in place. Get pulley inside the chain loop and meshed with the chain then bolt the pulley into place.

Step 5: Head gasket

Tools: N/A

Fasteners:

2x 7 mm sleeve of length 14 mm

2x 7 mm sleeve of length 12 mm

1x flanged sleeve

1x 19 mm rubber spacer

1x 17 mm rubber spacer

1x 26 mm washer

1x 15 mm washer

Difficulty: 1 This only requires sliding parts down the copper colored rods.

a. First slide the head gasket on so that the all the holes on the gasket line up with the holes on the cylinder housing. There is a rectangular hole that should line up with the timing chain slot and a larger circular hole at the bottom of the housing that lines up with a hole in the gasket.

b. Position yourself so that you are looking directly at the front of the engine (You should be able to see the piston head). The top two rods each have one 12 mm sleeves and the bottom two rods each have a 14 mm sleeve. The flanged sleeve goes in the bottom hole.

c. The 15 mm washer goes around the bottom left rod.

d. The 19 mm rubber spacer goes around the top left rod.

e. The 17 mm rubber spacer goes to the top right rod.

f. The 26 mm washer goes to the bottom hole. However it must be held in place until the valve assembly is put over it to hold it in place.

Step 6: Valve Assembly

Tools: 8, 9, 10, and 17 mm wrenches

Fasteners:

2x 9 mm nuts

4x hexagonal flanged cap nuts

4x 8 mm washers

2x 8 mm hexagonal full thread tap bolts of length 20 mm

1x 10 mm hexagonal full thread tap bolts of length 110 mm

1x 6 mm washer

1x 10 mm hexagonal full thread washer bolt with Phillips slot

3x 8 mm hexagonal full thread bolts

Difficulty: 3 This is a straight forward step that for the most part only requires making sure that bolts are being used in the right spots. The difficult part is getting the timing chain around the sprocket.

a. Slide the valve assembly onto the four rods. Make sure the threaded hole is lined up with the threaded hole on the cylinder housing. Screw the bolt with the Phillips slot into this hole.

b. Attaching the timing sprocket could require two people. First get the sprocket threaded with the chain. Then line up the three holes on the sprocket with the three holes on the valve assembly. Use the 8 mm bolts to screw it in place. Note: The holes are not evenly spaced around the center of the sprocket. This means that there is a specific way to get the holes to line up. One person should hold the sprocket while the other rotates the plate on the valve assembly until all the holes line up.

d. Slide the octagon shaped cover onto the copper colored rods. Screw a capped nut onto each of the rods.

e. Screw the rectangular plate to the left side (when viewing the engine from the front) with two 8 mm bolts. The center hole is for the 110 mm bolt and goes through the whole assembly. Hold the circular cover to the right side of the engine (covering the timing sprocket) and slide the bolt through. It tightens into the circular cover.

f. Screw in the spark plug on the right side of the valve assembly. The slot is set deep into the housing.

Step 7: Drive Chain Gear

Tools: 10 mm wrench

Fasteners:

2x 10 mm hexagonal full thread bolts bolt

1 sprocket spacer

Difficulty: 2 The spacer needs to be lined up with the bolt slots on the sprocket.

a. Slide the sprocket onto the drive shaft. The inner teeth should lock it in place.

b. Slide the spacer on. The teeth force it to slide on in a set way, but there is a slot on the shaft where there are no teeth. Use this space to rotate the spacer until the holes line up with those on the sprocket.

c. Screw the 10 mm bolts in to fasten it in place.

Step 8: Magneto Stator Plate

Tools: #4 Phillips head screwdriver

Fasteners:

2x flat head Phillips bolts

Difficulty: 1

a. The stator plate fits into the “window” mentioned earlier. Line up the holes and make sure the two arms of the stator plate are at the bottom right side.

b. Screw in the flat head bolts.

Comparison: This step was much more difficult in dis-assembly because the bolts were very tight. Phillips head screws tend to slip which made it difficult to get the bolts out because they kept stripping.

Step 9: Stator Plate Wiring

Tools: #2 Phillips head screwdriver

Fasteners:

4x round Phillips head bolt

Difficulty: 4

a. Screw the wire coil into the top and right prongs on the stator plate. Make sure it isn’t screw in backwards. The metal sections on the wire coil that get screwed to the plate have a rounded edge. This rounded edge should be facing outwards.

b. The black plastic part of the wiring with the metal nub slides into the two arms on the stator plate. The nub should be pointing toward the center of the plate. Screw it into the arms with two bolts.

c. There is a rubber part holding the wires together that has two flanges. There is a notch in the transmission housing where this rubber part fits into. The wires with plastic part at the end should be coming out of the transmission housing.

d. The wires have metal brackets at two locations. These brackets need to be spot welded back into place. The metal bracket closer to the rubber section has a hole on it that must be pressed over a metal bulb near the top of the transmission housing. Weld it in place after.

e. The second metal bracket is just welded into place between the two arms of the stator plate. Note: For the groups reassembly a spot welder was not available. The part still needed to be grounded so it was screwed to one of the arms with the black plastic part.

Comparison: This part was more difficult than the disassembly because it required the brackets to be spot welded. It also requires more precision in getting all the wiring together. Prying the brackets off and pulling all the wiring out is a much simpler task.

Step 10: Magneto

Tools: 17 mm wrench

Fasteners:

17 mm washer nut

Difficulty: 2 The nut must be tightened a lot.

a. Slide the magneto onto the crank shaft. Make sure no wires are interfering with the rotation of the magneto. Put the nut on and tighten. Either clamp down on or have someone hold the clutch to keep it from rotating.

Step 11: Shifting mechanism

Tools: N/A

Fasteners: N/A

Difficulty: 1

a. Attach the select lever to the flanged shaft on the magneto side of the transmission. It should be parallel

b. The arm slides onto the same flanged shaft on the other side of the transmission. The cylindrical protrusion faces towards the clutch and should be over the clutch.

c. The round part of the mechanism slides into the center of the clutch so that the mandibles straddle the cylindrical section of the arm.

d. The spring fits inside the sleeve which then fit into the center of the round section (put it in spring first).

Step 12: Outer Right Transmission Housing (clutch cover)

Tools: 10 mm wrench

Fasteners:

1x 10 mm hexagonal washer bolt of length 80 mm

2x 10 mm hexagonal washer bolts of length 64 mm

5x 10 mm hexagonal washer bolts of length 40 mm

Difficulty: 3 The bolts belong to certain slots depending on size. The shifting mechanism underneath the housing makes it difficult to slide on because it needs to be lined up properly.

a. Inside the section of the clutch cover that will be covering the clutch there is a rotating part with three arms. These arms fit inside the “waves” in the round part of the shifting mechanism. When the housing is being put on have some pushing the select lever while the cover is being pushed in. This will allow the waves to line up with the three armed part on the cover.

b. Screw in the bolts in the same fashion as they were in step 1 (fitting bolts into the correct sized slots).

Step 13: Outer Right Transmission Housing (magneto cover)

Tools: 10 mm wrench

Fasteners:

1x 10 mm hexagonal washer bolt of length 28 mm

1x 10 mm hexagonal washer bolt of length 35 mm

Difficulty: 1

a. There are only two bolts to be screwed in. The longer bolt goes to the longer slot and the shorter bolt goes to the shorter slot.

Step 14: Oil Drain Bolt

Tools: 17 mm wrench

Fasteners: (this is a fastener)

Difficulty: 1

a. Flip the engine over. There should be a slot for a bolt still open. Screw in and tighten the bolt.

Step 15: Kick Start

Tools: 10 mm wrench

Fasteners:

1x 10 mm hexagonal full threaded tap bolt

Difficulty: 1

a. Attach the kick start lever to the splined shaft that is still visible. Make sure the foot rest for the lever folds out and away from the bike. The lever should also be facing towards the rear of the bike. The angle of attachment can be whatever is most comfortable to the rider.

Step 16: Plastic oil Plug

Tools: N/A

Fasteners: N/A

Difficulty 1

a. Screw in the plug to the slot by the kick start lever.

Discussion

The product was not tested to see if it would still run (do to time and monetary constraints). The group was unable to get the wiring back to the exact way it was before disassembly. This would most likely be the source of any problem with the engine. There could be contact with the wires to the magneto to not spine properly and cause wearing on the wires. This could be fixed by welding the brackets to their original places where they were out of the way from the rest of the components. We were able to put all the other components of the engine together the way it was originally was. However, our group was only responsible for the engine and cannot be certain whether other components of the bike outside the engine would cause the dirt bike to not run properly, or not run at all.

The same tools were used for both assembly and dis-assembly. Had the group decided to pull off the gears of the transmission a tool would have been necessary to re-press them on. This would be one of the only changes in tools necessary. Also, though the same tools were used not all were used in the same way. The flat head screwdriver, which was used for prying the transmission housings apart was not needed for that purpose for reassembly.